Koiwa Iris Festival

An annual rainy season highlight at the Koiwa Iris Garden, an expansive park out on the Edo River's western banks, this festival sees around 100 varieties of iris flowers – a whopping 50,000 in total – burst into bloom in late May. Booths selling snacks, drinks and flowers are set up on the colourful grounds, which can also be admired from the passing Keisei line trains nearby.